Benthic macroinvertebrate bycatch in the snail dufresnei (Donovan) fishery from the Uruguayan continental shelf

1,2 1 3 GUSTAVO RIESTRA , JUAN PABLO LOZOYA , GRACIELA FABIANO , ORLANDO 3 4 SANTANA & DANIEL CARRIZO

1 Dirección Nacional de Recursos Acuáticos, Montevideo-Uruguay. e-mail: [email protected] 2 Museo de Historia Natural “Dr. Carlos Torres de la Llosa”, Uruguay. 3 Dirección Nacional de Recursos Acuáticos, La Paloma-Uruguay. 4 Instituto de Investigaciones Químicas y Ambientales de Barcelona, Spain.

Abstract. The benthic macroinvertebrate fauna associated with the fishery of “caracol fino” (, ) was analysed during three fishery cruises in the Uruguayan continental shelf. Species composition, richness, diversity and qualitative dominance were estimated from the examination of the bycatch of 172 fishing hauls using a double bottom otter trawl. In the Uruguayan Atlantic waters 55 species of macroinvertebrates were associated with Z. dufresnei, being molluscs and the dominant taxa in species number and frequency of occurrence. Two gastropods (Adelomelon beckii and Tonna galea), two decapod crustaceans ( spinosa and Propagurus gaudichaudii), one asteroid (Astropecten brasiliensis), and one Actiniaria ind. were the most representative species in the “caracol fino” bycatch. Further studies considering unexplored bathymetric gradients are strongly recommended, they will help to fill our current gap in the knowledge of the macrobenthic diversity in the Uruguayan continental shelf.

Key words: Benthic macrofauna, fauna associated, diversity, qualitative dominance, Uruguay.

Resumen. Captura incidental de macroinvertebrados bentónicos en la pesquería de caracol fino Zidona dufresnei en la plataforma continental uruguaya. La fauna de macroinvertebrados bentónicos asociada a la pesquería de “caracol fino” Zidona dufresnei (Mollusca, Gastropoda) en la plataforma continental uruguaya fue estudiada en base a tres cruceros de pesca. Se determinó la composición y riqueza específica, diversidad y dominancia cualitativa mediante el análisis de 172 lances efectuados con red de arrastre de fondo. Se registraron 55 especies de macroinvertebrados asociadas a Z. dufresnei en el Atlántico uruguayo, resultando los moluscos y los crustáceos los taxa dominantes en número y frecuencia de ocurrencia. Dos gasterópodos (Adelomelon beckii y Tonna galea), dos crustáceos decápodos (Libinia spinosa y Propagurus gaudichaudii), un asteroideo (Astropecten brasiliensis), y un Actiniaria ind. fueron las especies más representativas en el bycatch del “caracol fino”. Se recomienda considerar nuevos gradientes batimétricos a los efectos de profundizar en el conocimiento de la diversidad macrobentónica en la plataforma continental uruguaya, en futuros estudios.

Palavras Clave: Macrofauna bentónica, fauna asociada, diversidad, dominancia cualitativa, Uruguay.

Introduction started to foresee the potential effects of the Bottom trawling and the use of other active fishery generalized disturbance of the sea floor due to the techniques disrupt marine bottoms in the same way growth in number and capacity of the fleet of bottom as logging affects forest ecosystems. Although it is trawlers (Watling & Elliot 1998). easy to recognize the effects of deforestation on Unrestricted fishery has different impacts on biological diversity and economic sustainability, marine ecosystems. Fishery has direct effects on concern for the loss of marine benthic habitats as a target species, reducing populations and stocks, result of fishery is far less common. In fact, it was affecting body size composition, and in some cases not until the middle of 1980’s that marine biologists spawning biomass. Moreover, it has also indirect

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Benthic macroinvertebrate bycatch in Zidona dufresnei Uruguayan fishery. 105 effects on predator-prey interactions, modifying Materials and Methods community structure, even generating temporal Study Area alternative states. A genetic selection of certain size The study was carried out in the classes and reproductive characteristics can also be north-eastern zone of the Uruguayan continental promoted, reducing or removing local stocks. Two shelf, between 34º20' - 35º22' Lat S and additional indirect perturbations associated with the 52º47' - 54º53' Long W, which represents the fishery are the bycatch or mortality of non-target most important fishing grounds for Zidona dufresnei species, and the reduction of habitat complexity, in Uruguay (DINARA 1997). The snail’s fishing particularly by bottom trawling (Kaiser et al. 2001). area is 30 to 70 m deep (Fig. 1), with sandy, muddy, Coastal macrobenthic communities are and occasionally rocky bottoms. This zone ecologically and economically important. They is influenced by the Malvinas and Brazil currents, provide a number of ecological services to mankind, plus a significant flow of fresh water from the Río not restricted to their role in the nutrient and organic de la Plata, which results in a peculiar matter recycling and as supporting biomass for hydrographical system (Guerrero & Piola 1997, (Caddy 1989). Ortega & Martínez ‘in press’). Given their relevance, identification of priority areas for marine conservation is critical, and in order to do so, basic knowledge on macrobenthic diversity is essential (Costello 1998). Exploratory studies on macrobenthic spatial patterns will contribute to a more responsible use of the marine environment (Van Hoey et al. 2004). Unfortunately, large portions of the coastal sea-bed, particularly in the Southern Hemisphere, remain poorly described, even in aspects as basic as species composition and habitat associations. The knowledge on faunal composition at the continental shelf will facilitate the prediction of potential impacts resulting from the development and growth of demersal fisheries, and will help to identify species potentially important Figure 1. Portion of the Uruguayan continental shelf where from a socio-economic point of view. fishing operations were carried out. Although several studies have described benthic communities in the South Atlantic region Sampling and laboratory methods (Buckup & Thomé 1962, Olivier et al. 1968, Escofet A total of 172 fishing hauls were undertaken et al. 1978, Roux et al. 1993, Capitoli 1996, Klein et during three commercial fishing trips (September al. 2001, Giberto et al. 2004), studies focusing on and November 2000, and May 2001), with scientific the benthic associations in the Uruguayan shelf are observers from the National Direction of Aquatic rather scarce (Juanicó & Rodríguez-Moyano 1975, Resources (DINARA) on board (Fig. 1). Milstein et al. 1976, Riestra 2000). Most of these Commercial outrigger trawlers, rigged to tow one previous studies focused on specific groups such as bottom otter trawl on each outrigger, were used in molluscs (Olivier & Scarabino 1972, Scarabino the three fishing trips where benthic 1973, Layerle & Scarabino 1984), decapod macroinvertebrate samples were taken (FAO 2005). crustaceans (Itusarry 1984), echinoderms (Barattini The trawls employed in the Z. dufresnei fishery had 1938, Bernasconi 1966, Lucchi 1985) and a 100 mm mesh size between opposed knots, a polychaetan annelids (Faget 1983). The focus of this mouth framed by a headline with floats providing a study encompasses an array of these invertebrates, maximum vertical opening of 1.5 m and a ground analyzing the benthic macroinvertebrates associated gear with chains, designed according to the bottom with the marine gastropod Zidona dufresnei condition to maximize the catches and protect the (Donovan, 1823), a volutid snail locally known as gear from damage. “caracol fino”, an important fishery resource in the Samples of the benthic macroinvertebrate Uruguayan continental shelf. bycatch were taken along each one of the three

Pan-American Journal of Aquatic Sciences (2006), 1 (2): 104-113 106 G. RIESTRA ET AL. campaigns and from each fishing haul, labelled and Bycatch fixed in 10% formaldehyde. Afterwards, in the The macroinvertebrate bycatch associated laboratory, the organisms collected were identified with the snail Zidona dufresnei fishery in the to the lowest possible taxonomic level, in most of Uruguayan continental shelf included 55 species the cases to species level. Sampling location (GPS), (data of all trips combined). These species belong to depth, speed and tow’s duration were also registered 5 phyla (Table I and II): mollusks (45%) and for each fishing haul. The total swept area (square (36%) were the most represented, nautical miles: nm2) in each campaign was followed by echinoderms (7%), cnidarians (7%) and calculated using the vessel speed, the maximum annelids (6%). horizontal gear opening and the duration of each trawl. Species richness and diversity The total number of species (S) identified Data analyses in September 2000 (S = 33 species) was larger than Mean species richness (Sm) for each in November 2000 (S = 31 species) and May 2001 trip was obtained from the species richness of (S = 25 species). However, the total number of each haul, based on the number of benthic species, the mean species richness and the mean macroinvertebrate species obtained. Mean diversity diversity did not differ significantly among (Shannon-Weaver 1979: H’m) for each campaign campaigns (Table II). was also calculated, using the diversity of each haul. A Chi-square test (χ2) was performed to test for Qualitative dominance differences in Sm and H’m between fishing trips Based on data of the three campaigns (Zar 1999). combined, the very abundant category was The relative importance of the different composed of the exploited target species species in the three trips combined was assessed Z. dufresnei (98%), Libinia spinosa Milne-Edwards, using Qualitative dominance (Bouderesque 1971) 1834 (89%) and Adelomelon beckii (Broderip, 1836) according to the frequency of occurrence (%). (87%). Tonna galea (Linnaeus, 1758), Propagurus Five categories were defined by this author: gaudichaudii Milne-Edwards, 1836, Actiniaria ind. occasional (0-20%), scarce (21-40%), common (41- and Astropecten brasiliensis Müller & Troschel, 1842, were abundant, 4 species were common, 60%), abundant (61-80%) and very abundant (81- 7 were scarce and 37 were occasional (Table III). 100%). Other species with very low occurrence Based on the presence-absence species (scarcely present in one haul), were not considered matrix, and employing a Similarity Coefficient (Q- for this analysis: Astrangia rathbuni Vaughan, 1906, mode), the similarity between species was calculated Aequipecten tehuelchus d’Orbigny, 1842, for each trip. An Unweighted Pair Group Method for Lithophaga patagonica (d’Orbigny, 1842), Arithmetic averages (UPGMA) (Legendre & Pododesmus rudis (Broderip, 1834), Pteria Legendre 1979) was applied as a technique of hirundo (Linnaeus, 1758), Transenpitar americana average linking. (Doello-Jurado, 1951), Bostrycapulus aculeatus (Gmelin, 1791), Crepidula sp., Polystira Results formosissima (E. A. Smith, 1915), Balanidae ind., The mean duration of campaigns was Heterosquilla platensis (Berg, 1900), Corystoides 13 days, with a maximum number of fishing hauls chilensis Lucas, 1844, Leucippa pentagona in September and May (59 hauls) and a minimum in Milne-Edwards, 1833, Ovalipes trimaculatus November (54 hauls). Mean haul duration (± SE) (De Haan, 1933), Pinnotheres sp. and Portunus was shorter in May (3.14 ± 0.12 hours) than in spinicarpus (Stimpson, 1871). November (3.38 ± 0.49 hours) and September (3.45 ± 0.46 hours). The shortest (1.00 hour) and the Similarity longest (4.35 hours) hauls occurred in May. Based on the cluster analysis, the highest However, mean haul speed (± SE) was faster similarity (> 93%) was found between Z. dufresnei, in November (3.1 ± 0.13 knots) than in May L. spinosa and A. beckii for both September (Fig. 2a) (2.8 ± 0.08 knots) and September (2.8 ± 0.15 knots). and November (Fig. 2b) campaigns. However, in The bottom swept area was larger in November May 2001, the highest similarity (90%) was (6.9 nm2) than in May (5.9 nm2) and September found between the fishing target species and T. (5.8 nm2). galea (Fig. 2c). Considering a level of similarity

Pan-American Journal of Aquatic Sciences (2006), 1 (2): 104-113 Benthic macroinvertebrate bycatch in Zidona dufresnei Uruguayan fishery. 107

Table I - Species composing of the benthic macroinvertebrate bycatch of the snail Zidona dufresnei fishery in the Uruguayan continental shelf.

Phylum Prunum martini (Petit, 1853) Class Anthozoa Tonna galea (Linnaeus, 1758) Alcyonaria ind. Zidona dufresnei (Donovan, 1823) Antholoba achates (Drayton, 1846) Class Cephalopoda Astrangia rathbuni Vaughan, 1906 Loligo sanpaulensis Brakoniecki, 1984 Phlyctenanthus australis Carlgren, 1950 tehuelchus d’ Orbigny, 1834

Phylum Annelida Phylum Echinodermata Class Polychaeta Class Asteroidea Aphrodita longicornis Kingberg, 1855 Asterina stelliffer (Möbius, 1859) Phyllochaetopterus socialis Claparède, 1870 Astropecten brasiliensis Müller & Troschel, 1842 Polychaeta ind. Luidia sp. Class Ophiuroidea Phylum Mollusca Ophiuroidea ind. Class Polyplacophora Chaetopleura angulata (Spengeler, 1797) Phylum Arthropoda Class Bivalvia Class Crustacea Aequipecten tehuelchus d’Orbigny, 1842 Balanidae ind. Corbula patagonica d’Orbigny, 1846 Callinectes sapidus Rathbun, 1896 Ennucula uruguayensis (E.A. Smith, 1885) Corystoides chilensis Lucas, 1844 Lithophaga patagonica (d' Orbigny, 1842) Farfantepenaeus paulensis (Pérez-Farfante, 1967) Mytilus edulis Linnaeus, 1758 Hepatus pudibundus (Herbst, 1785) puelchana d' Orbigny, 1842 Heterosquilla platensis (Berg, 1900) Panopea abbreviata Valenciennes, 1839 Leucippa pentagona Milne-Edwards, 1833 Pitar rostratus (Koch, 1844) Leurocyclus tuberculosus Milne-Edwards & Lucas, 1842 Pododesmus rudis (Broderip, 1834) Libinia spinosa Milne-Edwards, 1834 Pteria hirundo (Linnaeus, 1758) Metanephrops rubellus (Moreira, 1905) Trachycardium muricatum (Linnaeus, 1758) Ovalipes trimaculatus (De Haan, 1933) Transenpitar americana (Doello-Jurado, 1951) Propagurus gaudichaudii Milne-Edwards, 1836 Class Gastropoda Peltarion spinosulum (White, 1843) Adelomelon beckii (Broderip, 1836) Persephona mediterranea (Herbst, 1794) Adelomelon brasiliana (Lamarck, 1811) Pinnotheres sp. Buccinanops cochlidium (Dillwyn, 1817) Platyxanthus crenulatus Milne-Edwards, 1879 Bostrycapulus aculeatus (Gmelin, 1791) Platyxanthus patagonicus Milne-Edwards, 1879 Crepidula sp. Pleoticus muelleri (Bate, 1888) Cymatium parthenopeum (von Salis, 1793) Portunus spinicarpus (Stimpson, 1871) Polystira formosissima (E.A. Smith, 1915) Scyllarides deceptor Holthuis, 1963

of 80%, the Actiniaria ind. and Buccinanops Discussion cochlidium were added to the original group, and an Some methodological constraints must be association between and A. considered before the discussion of the results. The brasiliensis appeared in September 2000 (Fig. 2a). objective of the fishing campaigns and mainly the Propagurus gaudichaudii, Pitar rostratus, T. galea, sampling procedure employed, which only caught Ostrea puelchana and A. brasliensis were included large macroepifauna (> 50 mm), not allow a comparison with previous studies in the region. in the initial similarity group in November 2000 The 55 species of benthic macro- (Fig. 2b), and P. gaudichaudii and L. spinosa were invertebrates that form the bycatch of the snail incorporated to the initial group in May 2001 Z. dufresnei’s fishery on the Uruguayan (Fig. 2c). Considering a 60% similarity level, continental shelf represent a lower species richness the same seven species were associated in the than for other areas of the Southeastern three campaigns: Z. dufresnei, A. beckii, T. galea, Atlantic region already described, such as the L. spinosa, P. gaudichaudii, A. brasiliensis and southern Brazilian Atlantic littoral (Klein et al. Actiniaria ind. (Figs. 2 a, b and c). 2001), the Rio de la Plata estuary and adjacent shelf

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Table II - Mean species richness (Sm ± SE), mean diversity (H’m ± SE), associated χ2 test statistics, and phyla composition (%) of the bycatch of the three fishing campaigns.

Sep 2000 Nov 2000 May 2001 12 ± 3.6 11 ± 2.5 9 ± 2.9 Mean species richness χ2 = 1.17; P = 0.56 2.5 ± 0.3 2.3 ± 0.3 2.2 ± 0.3 Mean diversity χ2 = 0.02; P = 0.99 Mollusca 43 46 52 Arthropoda 33 32 28 Phyla Echinodermata 9 13 8 composition Annelida 9 6 8 Cnidaria 6 3 4 waters (Giberto et al. 2004), and the Mar del Plata chosen: two gastropod molluscs (A. beckii and (Argentina) region (Roux et al. 1993). It must be T. galea), two decapod crustaceans (L. spinosa and taken into account that the lack of previous studies P. gaudichaudii), one asteroid echinoderm in the region, regarding the macrobenthic bycatch in (A. brasiliensis) and one Actiniaria ind. These the Z. dufresnei’s fishery, does not results agree partially with those of Buckup & allow an adequate comparison. Nevertheless, the Thomé (1962), who considered Z. dufresnei, Shannon-Weaver diversity index obtained for the L. spinosa and Adelomelon brasiliana as very Uruguayan continental shelf was in agreement with frequent species in the Rio Grande do Sul those documented for the Argentinean zone (Roux et continental shelf (Brazil) between 20 and 50 m deep. al. 1993, Roux & Bremec 1996). In the present study, A. brasiliana did not follow The macroinvertebrate community defined that association, being classified as an occasional as the bycatch of the Z. dufresnei’s fishery showed species. faunal components of warm-temperate (e.g., Despite L. spinosa and the hermit H. platensis, L. pentagona and P. muelleri) and Dardanus arrosor insignis were documented as very cold-temperate regions (e.g., P. gaudichaudii and P. frequent species for that zone by Itusarry (1984), spinosulum) (Boschi et al. 1992). This could be only the first one was founded in our study. The explained by the convergence of different water unexpected absence of this could be masses with contrasting thermohaline that partially ascribed to a potential error in the characterize the Uruguayan continental shelf identification of the hermit . In the other hand, (Ortega & Martínez ‘in press’). Tropical Water the frequent occurrence of A. brasiliensis is in carried southward by the Brazil Current agreement with the results of Juanicó & Rodríguez- (Sverdrup et al. 1942), Subantarctic Water advected Moyano (1975) for the south-eastern zone of La northwards by the Malvinas Current (Bianchi et al. Paloma (Rocha, Uruguay), where it was the second 1993) and Coastal Waters mainly from the Rio de la faunal component, only preceded by Mytilus edulis, Plata estuary, result in this peculiar hydrographical between 35 and 50 m deep. This asteroid was also system (Guerrero & Piola 1997, Ortega & Martínez very well represented in the Euvola ziczac shell ‘in press’). banks at the Brazilian south coast (20 to 50 m depth) The highest qualitative dominance values (Klein et al. 2001). The very low frequency obtained corresponding to molluscs and crustaceans for Mytilus platensis, Lithophaga patagonica, are in agreement with those found for the Bostrycapulus aculeatus, and Chaetopleura isabellei Argentinean and Brazilian continental shelves could be explained by the fact that these species are (Bastida et al. 1992, Roux et al. 1993, Roux & highly associated with hard bottoms (Roux et al. Bremec 1996, Bremec & Roux 1997, Klein et al. 1993), where the Uruguayan Z. dufresnei fishery 2001), although those authors used different does not operates. sampling methods. A biological association between the snail To characterize the macrobenthic B. cochlidium and the actinian Phlyctenanthus invertebrates associated with the snail Z. dufresnei in australis, described by Pastorino (1993) for the Uruguayan continental shelf, six species with a Patagonian coastal waters (Argentina), was also coefficient of similarity higher than 60% were observed in our study. Other associations that were

Pan-American Journal of Aquatic Sciences (2006), 1 (2): 104-113 Benthic macroinvertebrate bycatch in Zidona dufresnei Uruguayan fishery. 109

Table III - Qualitative Dominance (%) (Bouderesque, 1971) of each species and their corresponding phylum: (A) Arthropoda, (An) Annelida, (C) Cnidaria, (E) Echinodermata, (M) Mollusca.

Category Species Phylum Qualitative dominance (%) Zidona dufresnei M 98.3 Very Abundant Libinia spinosa A 89.2 Adelomelon beckii M 86.6 Tonna galea M 74.7 Abundant Propagurus gaudichaudii A 74.0 Actiniaria ind. C 71.0 Astropecten brasiliensis E 68.1 Buccinanops cochlidium M 56.3 Common Aphrodita longicornis An 55.4 Platyxanthus crenulatus A 48.8 Octopus tehuelchus M 43.1 Pitar rostratus M 39.4 Asterina stellifer E 35.8 Platyxanthus patagonicus A 33.5 Scarce Phyllochaetopterus socialis An 33.1 Leurocyclus tuberculosus A 31.5 Ostrea puelchana M 24.6 Farfantepenaus paulensis A 23.1 Loligo sanpaulensis M 17.2 Cymatium parthenopeum M 13.6 Metanephrops rubellus A 11.6 Mytilus edulis M 10.0 Peltariom spinosulum A9.6 Chaetopleura angulata M8.9 Luidia sp. E6.2 Adelomelon brasiliana M5.5 Panopea abbreviata M4.9 Trachicardium muricatum M4.0 Ophiuroidea ind. E3.1 Persephona mediterranea A2.4 Ennucula uruguayensis M1.7 Ovalipes trimaculatus A1.7 Pleoticus muelleri A1.7 Polychaeta ind. An 1.2 Alcyonaria ind. C 1.1 Astrangia rathbuni C0.6 Occasional Aequipecten tehuelchus M0.6 Balanidae ind. C 0.6 Bostrycapulus aculeatus M0.6 Callinectes sapidus A0.6 Corbula patagonica M0.6 Crepidula sp. M0.6 Corystoides chilensis C0.6 Hepatus pudibundus A0.6 Heterosquilla platensis A0.6 Leucippa pentagona C0.6 Lithophaga patagonica M0.6 Pinnotheres sp. C0.6 Pododesmus rudis M0.6 Polystira formosissima M0.6 Portunus spinicarpus C0.6 Prunum martini M0.6 Pteria hirundo M0.6 Transenpitar americana M0.6 Scyllarides deceptor A0.6

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T.galea A .longicornis a Z.dufresnei L.spinosa A .beckii Actiniaria ind. B.cochlidium O.tehuelchus A .brasiliensis P.gaudichaudii O.puelchana P.crenulatus L.sanpaulensis L.tuberculosus F.paulensis P.socialis C.parthenopeum A .stellifer P.rostratus P.spinosulum M.rubellus M.edulis P.patagonicus P.abbreviata C.angulata P.mediterranea A .brasiliana Pinnotheres sp. S.deceptor Ophiuroidea ind. T.muricatum Alcyonaria ind. H.pudibundus 0 20 40 60 80 100

M.edulis b M.rubellus T.muricatum E.uruguayensis P.muelleri F.paulensis O.tehuelchus P.crenulatus A.magna.longicornis Z.dufresnei A.beckii L.spinosa P.gaudichaudiP.gaudichaudii P.rostratus T.galea O.puelchana A.brasiliensis P.patagonicus A.stellifer Luidia sp. C.parthenopeum CephalodiscusP.socialis sp. O.trimaculatus Alcyonaria ind. C.patagonica L.sanpaulensis C.sapidus Ophiuroidea ind. C.angulata A.brasiliana P.mediterranea 0 20 40 60 80 100

F.F.paulensis c C.C.angulata C.C.partenopheum P.P.martini P.martiniP.spinosulum M.M.edulis O.O.tehuelchus B.B.cochlidium P.P.crenulatus A.brasiliensis. A.stellifer. Z.Z.dufresnei T.T.galea P.P.gaudichaudii L.L.spinosa Actiniarianthozoa ind. A.becki. i L.L.tuberculosus A.longicornis. CephalodisP.socialis c O.O.puelchana M.M.rubellus P.P.abbreviata A.brasiliana. P.P.rostratus 0 20 40 60 80 100 Fig. 2 - Species dendrogram (UPGMA). Dotted vertical line represents the 90% of similarity between species: a) September 2000, b) November 2000 and c) May 2001.

Pan-American Journal of Aquatic Sciences (2006), 1 (2): 104-113 Benthic macroinvertebrate bycatch in Zidona dufresnei Uruguayan fishery. 111 already observed for Argentinean waters were also E.W. Langton, A.N. Shepard & I.G. Babb. found in the Uruguayan continental shelf: 1996. The impacts of mobile fishing gear on A. brasiliana and the actinia Antholoba achates seafloor habitats in the Gulf of Maine (Luzzatto & Pastorino 2006) and Libinia spinosa (Northwest Atlantic): implications for with A. achates (Acuña et al. 2003). conservation of populations. Reviews in Even if in the last years the number of Fisheries Science, 4 (2): 185 - 202. vessels in the fishery of “caracol fino” has Barattini, L. 1938. Equinodermos uruguayos. substantially diminished, the fishery is still open and Boletín del Servicio Oceanográfico y de the bottom is still heavily trawled. Fishing gears Pesca, 17-29. alters seafloor habitats and understanding the extent Bastida, R., A. Roux & Martínez, D. 1992. Benthic of these impacts, and the effects on populations of communities of the Argentine continental living marine resources, is needed to properly shelf. Oceanologica Acta, 15 (6): 687 - 698. manage current and future levels of fishing effort Bernasconi, I. 1966. Los equinoideos y asteroideos (Auster et al. 1996). The knowledge of the colectados por el Buque Oceanográfico R/V macroinvertebrate diversity results essential for a “Vema”, frente a las costas argentinas, sustainable fisheries management and the uruguayas y sur de . Revista del development of potentially valuable resources. Museo Argentino de Ciencias Naturales Because of the lack of pristine sites, where the use of active fishing is prohibited, no empirical studies that “Bernardino Rivadavia”, Tomo IX (7): could demonstrate population level effects of bottom 147 - 175. trawling, have been conducted so far. If marine Bianchi, A., C. Giulivi & Piola, A. 1993. Mixing fisheries management is to evolve toward an in the Brazil–Malvinas Confluence. Deep ecosystem or habitat management approach, Sea Research Part I, 40 (7): 1345 - 1358. experiments are required on the effects of habitat Boschi, E., C. Fischbach & Iorio, M. 1992. change, both anthropogenic and natural (Auster et Catálogo ilustrado de los crustáceos al. 1996). According to the current gap in the estomatópodos y decápodos marinos de knowledge of macrobenthic diversity in the Argentina. Frente Marítimo 10 (Sec. A): 7 Uruguayan continental shelf, further investigations - 94. concerning unexplored bathymetric gradients with Bouderesque, Ch. 1971. Méthodes d’étude systematic samplings and experiments are strongly qualitative et quantitative du benthos (en recommended. particulier du phytobenthos). Tethys 3 (1): 79 - 104. Acknowledgments Bremec, C. & Roux, A. 1997. Resultados del The authors wish to thank the collaboration of the análisis de una campaña de investigación fishing companies as well as to the captains and pesquera, sobre comunidades bentónicas crews of the snail vessels. We also express our asociadas a bancos de mejillón (Mytilus sincere thanks to F. Scarabino for his comments on edulis platensis D’Orb.) en costas de Buenos the determination of species and for bibliography. Aires, Argentina. Revista Investigación y We also gratefully acknowledge Dr. M. Zamponi for Desarrollo Pesquero 11: 153 - 166. his identification of the actinian. The authors want to Buckup, L. & Thomé, J. 1962. I Campanha thank Dr. E. Spivak, Dr. P. Quijón, Dr. S. Acevedo oceanográfica do Museu Rio Grandense de and Dr. McCormark for the critical revision of the Ciências Naturais – a viagem do “Pescal II” manuscript and especially to Dr. Alexandre Garcia en julho de 1959. Iheringia 20: 1 - 42. and Dr. Gonzalo Velasco, Editorial Board of Pan- Caddy, J. 1989. Recent developments in research American Journal of Aquatic Sciences. and management for wild stocks of bivalves and gastropods. p. 665-699 In: J. Caddy (Ed), Marine Invertebrate Fishery: their References assessment and management. John Wiley Acuña, F., A. Excoffon & Scelzo, M. 2003. Sons, London. 699 p. Mutualism between the Capitoli, R. 1996. Continental shelf benthos. Antholoba achates (Drayton, 1846) (Cnidaria: Chapter 6, p. 117-120. In: U. Seeliger, C. Actiniaria: Actinostolidae) and the spider crab Odebrecht & J.P. Castelo (Eds), Libinia spinosa Milne-Edwards, 1834 Subtropical Convergence Environments. (Crustacea: , Majidae). Belgian Springer-Verlag, Berlín. 120p. Journal of Zoology, 133 (1): 85 - 87. Costello, M. 1998. To know, research, manage and Auster, P.J., R.J. Malatesta, R.W. Langton, L. conserve marine biodiversity. Oceanis 24: Watling, P.C. Valentine, C.L.S. Donaldson, 25 - 49.

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Received June 2006 Accepted October 2006 Published online December 2006

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